The Prince of Wales told a schoolboy it "was really fun being a grandfather" to Prince George, who was born on Monday afternoon.
Charles met George Austin, nine, as he opened a new garden at Kemble railway station in Gloucestershire, two days after he met his grandson for the first time.
George and sister Lucinda, four, were at the station - the closest to the Prince's Highgrove home - with their grandparents.
George, who lives in Wimbledon, south west London, said: "I was asking him about the baby and he said it was great meeting him at the hospital.
"He said it was really fun being a grandfather."